1. Field of the Invention
The present invention relates to a vehicle travel control system adapted to detect an object within an estimated locus of a subject vehicle and to control the travel state of the subject vehicle in accordance with the positional relationship between the object and the subject vehicle.
2. Description of the Related Art
A conventional object recognizing process is known from Japanese Patent Application Laid-open No.8-240660, which distinguishes a moving object, such as a preceding vehicle, from a stationary object, such as a guard rail, by merging data from select objects of a plurality of objects detected by a radar system mounted on a subject vehicle. The positions of the select objects are closer to one another and the traveling speeds of the select objects relative to the subject vehicle have a variation within a predetermined range.
When a small-sized vehicle, such as an automobile, is traveling ahead of a subject vehicle and a large-sized vehicle, such as a carrier car, is traveling side by side with the small-sized vehicle, there is a possibility in the conventional object recognizing process that the respective data for the small-sized vehicle and the large-sized vehicle are merged and the two vehicles are misrecognized as a single vehicle. In such a case, the position of both vehicles is recognized by the conventional object recognizing process as the position of the large-sized vehicle because of a difference between the body size of each vehicle. It follows that the small-sized vehicle, traveling within an estimated locus of the subject vehicle, is not recognized and only the large-sized vehicle, traveling outside the estimated locus of the subject vehicle, is recognized. As a result, when the subject vehicle approaches both vehicles or the large-sized vehicle changes its travelling course so that the large-sized vehicle deviates from a range detectable by the radar system, the merged data for the small-sized and large-sized vehicles is separated and the small-sized vehicle is suddenly recognized within the estimated locus of the subject vehicle. As a result, there is a possibility that the braking ability of the subject vehicle to prevent a collision between the subject vehicle and a preceding vehicle is retarded.
It is an object of the present invention to overcome the above-described conventional object recognizing process.
It is also an object of the present invention to ensure that data for a plurality of objects in front of the subject vehicle are prevented from being inappropriately merged, so that control of the vehicle is properly executed.
To achieve at least the above objects, according to a feature of the present invention, there is provided a travel control system for a vehicle, including a transmitting/receiving means that transmits an electromagnetic wave toward a predetermined region in a direction of traveling of a subject vehicle and receives a wave reflected from an object within the predetermined region. An object information calculating means calculates a position of the object relative to the subject vehicle based on the results of wave transmission and reception by the transmitting/receiving means. A uniting means unites a plurality of objects into one target object based on at least the positions of the plurality of objects when the plurality of objects are detected within the predetermined region. A locus estimating means estimates a future travel locus for the subject vehicle. A vehicle control means controls the traveling state of the subject vehicle in accordance with the positional relationship between the target object and the subject vehicle when the target object united by the uniting means is within the estimated locus. The travel control system further including a separating means for separating the target object into separate (i.e., different)target objects that are inside and outside the locus estimated for the subject vehicle by the locus estimating means when the plurality of objects united by the uniting means are inside and outside the estimated locus of the subject vehicle.
With the above arrangement, when the plurality of objects detected by the transmitting/receiving means are united into a single target object, if the plurality of objects united into the single target object are inside and outside the estimated locus of the subject vehicle, the single target object is separated into separate target objects that are inside and outside the estimated locus of the subject vehicle. Therefore, target objects erroneously united into a single target object can accurately be recognized as separate objects, thereby properly executing control of the subject vehicle based on the positional relationship between the target objects within the estimated locus and the subject vehicle.
According to another feature of the present invention, the uniting means unites a plurality of objects within a predetermined region that is established based on one of the plurality of objects.
With the above arrangement, the objects within the predetermined region are detected and a plurality of objects that are originally separate are prevented from being united into a single target object.
According to additional features of the present invention, the travel control system further includes a position outputting means for outputting a representative position of the single target object united by the uniting means on the basis of the position of an object existing in a smaller region established in the predetermined region at a location closer to the subject vehicle.
With the above arrangement, the smaller region is established within the predetermined region at a location closer to the subject vehicle and the representative position of the target object based on the position of the object within the smaller region. Therefore, the representative position of the target object is established at a point that is as close as possible to the subject vehicle.
According to additional features of the present invention, when a plurality of objects exist in the smaller region, the position outputting means outputs a position that is central relative to the positions of two objects that are located at laterally opposite ends of the smaller region as the representative position.
With the above arrangement, the position central to the positions of the two laterally opposite objects within the smaller region is output as the representative position of the target object. Thus, the position of the target object is appropriately determined by the representative position.
According to yet more features of the present invention, when at least one of the plurality of objects is within the predetermined region that does not include the smaller region and is within the estimated locus, the separating means separates the one object as a target object.
With the above arrangement, a different target object is separated from the original target object once united on a condition that the separated different target object is within the predetermined region that does not include the smaller region. Therefore, different target objects, which are not required to be separated, are prevented from being separated from the original target object.
According to additional features of the present invention, the separating means separates, as a target object, an object located at a distance equal to or larger than a first predetermined distance toward the estimated locus on the basis of one of the objects original to output the representative position, which is closest to the estimated locus.
With the above arrangement, the object existing at the distance equal to or larger than the first predetermined distance toward the estimated locus on the basis of one of the objects existing in the smaller region is separated as a different target object from the original target object. Therefore, the separating of target objects, which are not required to be separated from the original target object, can be prevented from being carried out by mistake.
An exemplary first predetermined distance is set at 0.8 m in embodiments, but it is within the scope of the invention that the distance may be set at any value.
According to additional features of the present invention, the travel control system includes, in place of the separating means, a re-separating means which is adapted, when two or more of the plurality of objects united by the uniting means exist within the estimated locus, to re-separate (or separate again) the objects spaced at a lateral distance equal to or larger than a second predetermined lateral distance apart from each other as a different target object.
With the above arrangement, if the lateral distance between the two or more objects to be separated as the different target object from the original target object due to the existence of the objects within the estimated locus is equal to or larger than the second predetermined distance, the two or more objects are re-separated or separated again as the different target object. Therefore, the object existing on the estimated locus of the subject vehicle can be separated further reliably as the target object.
An exemplary second predetermined distance is set at 0.8 m in the embodiments, but it is within the scope of the invention that the distance may be set at any value.
According to yet more features of the present invention, the travel control system includes, in place of the separating means, a re-separating means which is adapted, when two or more of the plurality of objects united by the uniting means exist within the estimated locus, to re-separate the objects spaced at a longitudinal distance equal to or larger than a third predetermined distance apart from each other as a different target object.
With the above arrangement, if the longitudinal distance between the two or more objects to be separated as the different target object from the original target object due to the existence of them within the estimated locus is equal to or larger than the third predetermined distance, the two or more objects are re-separated as the different target object. Therefore, only objects required to be separated as a different target object can be reliably separated further.
An exemplary third predetermined distance is set at 3.0 m in the embodiments, but it is within the scope of the invention that the distance may be set at any value.
Also, the herein described millimeter-wave radar system in the embodiments may include and correspond to the transmitting/receiving means of the present invention.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.